Patent GB-627508-A (GB)
Title: Recoiling damper for improving the suspension of vehicles
IPC: F16F9/26
Filed: 1946-09-07
Abstract: 627,508. Hydraulic shock-absorbers. HELBIG, M. Sept. 7, 1946, No. 26958. Convention date, April 9. [Class 108 (iii)] A hydraulic damping device for vehicle suspensions comprises a pair of connected pistons, and corresponding cylinder forming liquid compression chambers which are interconnected by conduits each having a throttling device which comprises a valve for admission, and a valve for escape of liquid from the corresponding chamber, the valves opening in opposite directions and being arranged coaxially with the admission valve forming a seat for the escape valve, the arrangement being such that the damping forces exerted by the device for movement away from an intermediate position of the pistons relative to the cylinders (corresponding to level running conditions of a vehicle) are zero, but subsequently increase progressively towards the end of the movement, while for movement towards the intermediate position the force increases and subsequently decreases. In the construction described, flow from a reserve space 11 into either cylinder chamber 9 through conduits 14, is controlled by a respective admission valve 24 seated in the piston and loaded by a spring 26. Flow in the reverse direction is controlled by an escapevalve 12 seated on the valve 24 and loaded by a spring 22 which bears on a shoulder 20 of a stem 18. The inner end of the stem 18 is connected with a groove 54 in the lower surface of the piston which in the central position of the piston 5 relative to the cylinder 1, communicates with the cylinder chamber 9 by means of a recess 29 in member 28 which is slidably mounted in an axial slot in the surface of the piston wall. Each end of the member 28 is received in a recess 44 in the respective cylinder head which is connected by a screw-controlled damping passage with the respective cylinder chamber. The operating shaft 3 drives the piston by an arm 6 having an involute profile engaging a spring-urged member 7. Operation.-On outward deflection in either direction from the neutral position, pressure is equal at either end of each stem 18 due to the passage afforded by the piston grooves 54. The valve 12 on the compression side of the i piston 5 thus lifts freely until piston movement isolates the groove 54 from the recess 29. Pressure of liquid trapped in the groove 54 increases with further deflection and places increasing load on the valve spring 22 thus causing progressively increasing damping action of the valve 12. Flow in the reverse direction through the valve 24 at the other end of the piston occurs freely throughout the stroke. On inward deflection the valve 12 at the other end of the piston comes into action with progressively increasing damping since the respective piston groove 54 is sealed. Shortly before the central position of the piston is regained, the groove 54 comes gradually into communication with a tapered end portion 58 of the recess 29. The member 28 tends to take up a position symmetrical relative to the central position of the piston 5 irrespective of changes of dead load of the vehicle or aircraft, due to the pressures developed in the chambers 44 at the respective ends of the member 28.